Void Ark

Expulsion - will create a large AoE under and around the boss. Run away to avoid this.

Electric Swipe - a large rear cone AoE that will apply a Paralysis debuff to anyone caught in it.

Electric Whorl - a room-wide AoE that inflicts Electrocution and Paralysis to anyone caught in it. There is a safe zone around the boss, so the group should stack on Cetus when this cast begins.

Primary attacks deal cleave damage, so the MT should face the boss away from the raid.

75%, Cetus will begin spawning Hybodus Pup adds. These adds will cast a long frontal column AoE and they should be killed ASAP. If you are targeted by one, then run towards it so that you can "shrink" the AoE telegraph.

65%, Cetus will start to spawn Hybodus adds. After killing them, Cetus will cast Body Slam, slamming into the arena at the location where the last add was killed. This will be immediately followed by Electric Whorl.

The boss will also target random party members with a target marker. These players need to move away from the rest of the raid, since they will be dropping large AoEs that deal ~8k damage and have a knockback effect. This can easily wipe the raid if ignored.

25%, Cetus will put up a shield and spawn four Hydrospheres. These adds must be killed in order to drop the shield. Killing the last add will result in Cletus immediately dropping the shield and performing a Body Slam on the location where that add died. The rest is a repeat of mechanics, so just burn the boss!

Forward Port Ventilator:

Clearing this room will require the group to split into their three respective parties. Mark the areas within the circles and near the center of the room, as these locations will be important later.

When the message "The void's taint begins slowly seeping into your soul" pops up, at least one member of each party must stand in the marked areas in order to ventilate the room.

Focus the Pagan Knot adds first and then the remaining adds. Two waves of Morbols will spawn near the end; focus the Pagan Knots first, followed by the Morbols, and then any remaining adds last.

This room is primarily a healer check, as there are a lot of status effects and DoTs to cleanse.

Irminsul and Sawtooth:

The MT should bring Sawtooth to the wall and face him away from the party.

Each boss will be immune to a certain type of damage. If your target is immune to your damage, focus the other one. The damage immunity is either magic or ranged DPS, and will randomize between the two.

Ark Ked adds will spawn throughout the fight and must be killed ASAP. If they are not killed in time, Irminsul will enrage and cast Rootstorm--dealing a LOT of damage and likely wiping the party.

Mucus Spray - Sawtooth will spray green mucus around himself. Anyone who gets caught in this will have the Seized debuff applied, paralyzing that player.

Mucus Bomb - similar to Mucus Spray, except a random player will be targeted. The targeted player should run away from the rest of the group to avoid hitting anyone else with the debuff. Tethers will spawn after Mucus Bomb if multiple people are caught in the AoE, so targeted people should spread to the arena edge. Another player needs to run through the tethers to remove the Seized debuff.

At random intervals, the ground will rumble and break. Move away from the ground before it breaks, as the roots from the tree will swallow you, dealing damage over time and preventing any actions from taking place.

Once Irminsul is around 5%, you can use LB to kill it and then Sawtooth after it dies.

Central Conveyance Unit:

This room contains a mini-boss named Blackguard, who isn't of much consequence. Focus on the adds that spawn and then burn Blackguard down.

Hell Hound - will cast Abyssal Cry, which must be stunned or bad things will happen.

Sepulture Gargoyle - will cast a long column AoE called Desolation. The cast is fairly long, so it is easily avoided.

Cuchulainn:

There are 4 raised platforms around the room. Take note of their location or mark them for future reference, because you will need to stand on these later.

Corrosive Bile - the boss will vomit a frontal AoE, constantly stacking poison on the target unless they move away. The MT should step aside or run behind the boss before this cast finishes to avoid dying. There will be no telegraph for this, so watch for the cast bar.

Flailing Tentacles - will periodically raise its tentacles and slam them to the ground, dealing massive damage to anyone hit. You can avoid this by going between the tentacles or putting enough distance between you and the boss.

Idol of Impurity - will spawn Gyrtower adds around the room. Kill these ASAP because each one adds an additional stack of Bleeding while it is up.

Bile Below - a room-wide AoE poison will fill the floor, followed by a shockwave. When this happens, get on one of the platforms ASAP or you will die.

Void Pact - will spawn Foobar adds on each platform in two waves and the boss will become invulnerable during this phase. Burn the adds immediately and watch for when the boss casts Beckon.

Beckon - will face one of the Foobar adds with a frontal AoE. You MUST drag the add out of this before the cast finishes, otherwise the boss will swallow the add and cast Bile Below.

Pestilence - the boss will spray the entire room with a poison AoE. The only safe area is directly on the boss, so stack on Cuchulainn when this cast begins.

Black Lung - will spawn orange orbs around the room. The tanks should run through these ASAP. If they aren't tanked in time then they will explode after a short period in a room-wide AoE, dealing a LOT of damage and eventually wiping the raid.

Echidna:

Will eventually split into three parts: Echidna, Dexter, and Sinister. All 3 should be tanked away from each other, so mark these areas at the beginning of the fight. These parts don't follow normal enmity rules, so Party A's tank will always get Echidna while B and C's tanks get Dexter and Sinister.

Demonic Descent - will mark a random player with a grey orb. The damage is shared amongst players for the follow-up attack, so group on this player to minimize damage from Echidna's dive bomb.

Sickle Strike - this is a tank buster and it does a LOT of damage.

Sickle Slash - a massive frontal line AoE that is easily avoided by going between the AoE markers.

Abyssal Reaper - the boss will spin and knock everyone in the vicinity back while doing a fair amount of damage and applying a Vulnerability Up debuff. Avoided by running away when this casts.

Petrifaction - will Petrify anyone facing the boss. Avoided by facing away from the boss when this casts.

At around 50%, the boss will start spawning adds. Kill these ASAP.

Flame Wreath - a large AoE emanating from the boss. The radius is quite large, so run away ASAP.